1. Field of the Invention
The present invention relates generally to the fields of protein chemistry and cancer therapy. More specifically, the present invention relates to antileukoprotease, a peptide inhibitor of stratum corneum chymotryptic enzyme, and its uses in carcinoma diagnosis and treatment.
2. Description of the Related Art
Proteases mediate specific proteolysis involved in processing of precursors of protein hormones, activation of regulatory enzymes in blood coagulation and complement activation, and the tissue rearrangement involved in tumor progression (1). In the process of tumor invasion and metastasis, proteases mediate the digestion of neighboring extracellular matrix components during initial tumor growth. This allows shedding of minor cells into the surrounding environment, providing the basis for invasion of basement membranes in target metastatic organs. Proteolytic digestion is also required for release and activation of many growth and angiogenic factors (2-4).
A large number of reports have demonstrated increased production of several classes of proteases, including matrix metalloproteases (MMP""s), cysteine proteases, aspartic proteases and serine proteases in tumor cells (5-9). The proteolysis of the extracellular matrix is a highly complicated process, which probably involves a cascade of events requiring a variety of proteases (10). In this cascade, the integrated capacity for extracellular matrix digestion, tumor cell invasion, and metastatic growth may be mediated by proteases with unique specificities. This hypothesis is supported by findings that some agents specifically inhibit one of these proteases to reduce tumor cell invasion (11,12).
Stratum corneum chymotryptic enzyme (SCCE) was originally isolated from a keratinocyte derived library and was identified as a serine protease (13,14). Analysis of mRNA showed that two transcripts of 1.2 kb and 2.0 kb were present, and abundant expression of the stratum corneum chymotryptic enzyme gene was restricted to human skin. Immunohistochemical studies confirmed that stratum corneum chymotryptic enzyme was a tissue-specific enzyme only expressed by the stratum corneum (15). The nucleotide sequence includes an open reading frame for a stratum corneum chymotryptic enzyme precursor protein consisting of 253 amino acids. This inactive precursor becomes proteolytically active after tryptic removal of a 7 amino acid peptide from the amino terminal end of the propeptide. Recent studies have revealed that stratum corneum chymotryptic enzyme appears to catalyze the degradation of intercellular cohesive structures between corneocytes in the outermost cornified layer of the skin and contributes to the cell shedding process at the skin surface (14, 16, 17). This process occurs possibly through the degradation of matrix components including the desmosomal protein desmoglein I.
Protease inhibitor antileukoprotease (ALP), also known as secretory leukocyte proteinase inhibitor (SLPI), has been identified as a potent inhibitor of leukocyte elastase, cathepsin G, chymotrypsin and trypsin (18). Antileukoprotease has been cloned from skin tissue and shown to be a specific inhibitor of the stratum corneum chymotryptic enzyme (SCCE) (17). This serine protease is produced and released into mucus by secretory cells in the parotid, bronchus, cervix and testicular glands (18). There, it is thought to play a physiological role in preventing the proteolytic degradation of these tissues. However, little has been known about the expression of antileukoprotease in human cancer tissues, including ovarian cancer.
The prior art is deficient in the lack of effective means of using antileukoprotease as a diagnostic or monitoring tool of carcinomas. The present invention fulfills this long-standing need and desire in the art.
The present invention demonstrates that antileukoprotease (ALP) is overexpressed in low malignant potential tumors and carcinomas in ovary, while little or no transcript is present in normal adult and fetal tissues. This indicates that antileukoprotease may be used as a diagnostic or monitoring tool of ovarian tumors.
In one embodiment of the present invention, there is provided a method of detecting an ovarian or ovarian-derived metastatic tumor in an individual suspected to have such a tumor, comprising the step of detecting the level of antileukoprotease in a test tissue, a secretion from a test tissue or the blood. If the level exceeds the mean basal level of antileukoprotease in nondiseased individuals by 2 standard deviations or more, the individual has an ovarian or ovarian-derived metastatic tumor.
In still another embodiment of the present invention, there is provided a method of treating an individual having a ovarian tumor by administering antileukoprotease to the individual.
In yet another embodiment of the instant invention, a method of preventing metastasis of an ovarian tumor is provided wherein antileukoprotease is administered to an individual having such a tumor.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention given for the purpose of disclosure.